In Vivo Subcutaneous Thermal Video Recording by Supersensitive Infrared Nanothermometers

Abstract

Some of the old and unrealizable dreams of biomedicine have become possible thanks to the appearance of novel advanced materials such as luminescent nanothermometers, nanoparticles capable of providing a contactless thermal reading through their light emission properties. Luminescent nanothermometers have already been demonstrated to be capable of in vivo subcutaneous punctual thermal reading but their real application as diagnosis tools still requires demonstrating their actual capacity for the acquisition of in vivo, time-resolved subcutaneous thermal images. The transfer from 1D to 2D subcutaneous thermal sensing is blocked in the last years mainly due to the lack of high sensitivity luminescent nanothermometers operating in the infrared biological windows. This work demonstrates how core/shell engineering, in combination with selective rare earth doping, can be used to develop supersensitive infrared luminescent nanothermometers. Erbium, thulium, and ytterbium core-shell LaF 3 nanoparticles, operating within the biological windows, provide thermal sensitivities as large as 5% °C −1 . This "record" sensitivity has allowed for the final acquisition of subcutaneous thermal videos of a living animal. Subsequent analysis of thermal videos allows for an unequivocal determination of intrinsic properties of subcutaneous tissues, opening the venue to the development of novel thermal imaging-based diagnosis tools.

Thermal Properties of Lipid Bilayers Determined Using Upconversion Nanothermometry

“…[21,22] In addition, several examples of luminescent materials have been proposed for in vivo temperature sensing applications, including Ag2S nanodots to monitor brain thermoregulation, [23] and lanthanide-doped nanoparticles for 2D subcutaneous dynamic thermal imaging. [24] The latter rely on the favorable optical properties of the lanthanide ions which includes the well-described process of upconversion. Upconversion is an anti-Stokes process by which near infrared (NIR) irradiation is converted into Ultraviolet-Visible and NIR emissions.…”

In Vivo Contactless Brain Nanothermometry

“…[14] As the emission of these probes shows a linear and reversible thermal quenching, temperature can be immediately extracted from an intensity analysis of fluorescence images. [15] This has been recently demonstrated in photothermal therapy experiments, where PbS-based QDs provided intratumoral temperature feedback in real time. [16] Preclinical brain research would benefit from the relatively easy implementation and low cost of NIR transcranial temperature sensing as a contactless brain thermometry technique.…”

Near‐Infrared Ratiometric Luminescent Thermometer Based on a New Lanthanide Silicate

“…For instance, Ximendes et al defined the thermo-metric parameter as the ratio between the emission intensities of Yb 3 + at 1000 nm, and Er 3 + at 1550 nm. [21] The ratios between the Ho 3 + and Er 3 + , [22,23] and Er 3 + and Nd 3 + , [24] near-infrared emissions have also been used for temperature sensing.…”

“…For instance, Ximendes et al defined the thermo-metric parameter as the ratio between the emission intensities of Yb 3 + at 1000 nm, and Er 3 + at 1550 nm. [21] The ratios between the Ho 3 + and Er 3 + , [22,23] and Er 3 + and Nd 3 + , [24] near-infrared emissions have also been used for temperature sensing.We have been interested in the exploration of new rareearth silicates, including dense, layered and microporous materials, that emit in the visible and near-infrared spectral ranges. [25][26][27] Some of the reported luminescence properties are unique.…”